Manual-6
DRIVER PROTECTION FINE TUNING
1. Determine the driver’s maximum continuous average power rating in watts (W) (specified by the manufacturer).
2. Determine the driver impedance “z” in ohms (specified by the manufacturer).
3. Using the data in steps (1) and (2) above, calculate the maximum signal level in dBu that the driver can handle.
Max dBu = 20*log(
√
(w*z)/.775).
4. Determine the gain of the amplifier in dB (if the amplifier has a level control , you may wish to measure the gain). If, i.e.,
you put 1V in, how many volts come out? Then convert to dB (20 log gain).
5. Subtract the gain of the amplifier in dB from the answer in step (3) to obtain the correct Threshold setting for the MC 22.
6. Set the MC 22 Ratio to 10:1.
NOTES:
Any change in amplifier sensitivity setting will effect the power limit to the driver.
If the MC 22 is placed just before the amplifier, no other system levels will effect the power limit setting.
Example:
1. Driver power rating: w = 100 watts.
2. Driver impedance: z = 4 ohms.
3. 20*log(
√
(w*z)/.775) = 28.2 dBu.
4. Amplifier gain is 30 dB ( 1 V in equals 31.6 V out).
5. Set the MC 22 THRESHOLD control to 28.2 dBu-30 dB = -1.8 dBu.
6. Set the MC 22 RATIO control to 10:1.
SOUND SYSTEM WITH COMPRESSION
Let’s run a stereo system with compression (see Figure 1
on the next page). For this example, we use a Rane Mojo MX
22 2-Way Crossover and a Mojo MQ 302 Stereo Equalizer
along with the MC 22 Stereo Compressor. Patch the MC 22
Compressor Inputs from the program source or mixer outputs,
and send the MC 22 Outputs to the system equalizer (if you
have one), and then on to the crossover inputs (if you have
one). Set the equalizer and crossover Inputs to unity gain. Set
the LINK switch to ON, and adjust the THRESHOLD and
RATIO controls to keep the entire system dynamic range
under control. Locating the compressor before the equalizer
results in correct spectral balance during compression.
DRIVER PROTECTION
To individually limit Low and High drivers in a biamped
system, connect the Crossover Low Output into one MC 22
Input, and the High Output into the other MC 22 Input. The
MC 22 Outputs go right to the respective low and high
frequency power amplifier inputs (see Figure 2 on the next
page). Be sure the LINK switch is OFF. Set the RATIO
controls to 10:1.
Assuming your input signal has peaks in excess of -20
dBu, you should be able to rotate the THRESHOLD controls
and see some GAIN REDUCTION meter action. You should
begin to hear the difference. Leave these controls at whatever
level is appropriate for your application. For the most precise
settings, see the section below.